[Koha-devel] Should the first 3 digits of cn_sort be sorted for dewey decimal?

[Michael Kuhn]

Hi Barton

 > ...and then sub-divisions of the thousands are done after the decimal
 > point  -- 001.1, 001.2, etc...
 >
 > as such, I don't think that callnumber 1.1 is a valid DDC number... it
 > lacks the class and hundred-level group, and should, for the purposes
 > of cn_sort, be converted to 001_100000000000000.
 >
 > (Numbers above are taken from
 > https://www.oclc.org/content/dam/oclc/dewey/DDC%2023_Summaries.pdf).

Looking deeper into it it seems I was just talking about the classic 
"decimal classification" which doesn't have leading zeroes. There are 
too many variants of it, one of them being the Dewey Decimal 
Classification / DDC - which actually seems to behave as you say, 
including leading zeroes. I wasn't aware of that difference. As far as I 
know the DDC is mostly used in the USA but also in Europe many peopöle 
are referring to "Dewey" when they actually mean their local decimal 
classification.

So I guess many libraries are filling the DDC fields with content that 
is actually not proper DDC but their own variant of a decimal 
classification (for example I would think in Europe it will often be 
another hairy variant of the Universal Decimal Classification / UDC that 
behaves the way I described - see 
https://en.wikipedia.org/wiki/Universal_Decimal_Classification).

Best wishes: Michael
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